#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
int main()
{
    int a = 0;
    int b = 0;
    int c = 0;
    int d = 0;
    scanf("%d%d%d%d", &a, &b, &c, &d);
    int x = a > b ? a : b;
    int y = c > d ? c : d;
    int z = x > y ? x : y;
    printf("%d\n", z);

    return 0;
}